Present day lighting devices for vehicles, such as headlamps, consist of a housing, a reflector, and a plastic diffusing screen. The reflector, if embodied as a separate component, is frequently screwed into the housing, and the diffusing screen is bonded into the lamp housing. For these headlamps, positioning ribs onto which the diffusing screen has been mounted are sprayed in the adhesive channel of the lamp housing. The previously injected adhesive is pushed to the side and used after polymerization as both a positioning means and as a sealant and adhesive. It is disadvantageous that the housing and the diffusing screen can still be displaced after mounting, thereby rendering positioning by means of gages ineffective. In addition, owing to the production tolerances in the fabrication of plastics, a geometric variance of the diffusing screen is to be expected relative to the housing, and is also a mounting tolerance between two components. In the case of motor vehicle design, undesirable gaps due to such tolerances can be seen. Furthermore, diffusing screens can be fastened directly in a mechanical fashion (for example, by stapling) and in this case the diffusing screen is connected directly to the adhesive channel of the lamp housing.
In addition, a range of lighting devices for motor vehicles and methods for producing them are known from the prior art; reference may be made to the following publications by way of example:
DE 197 22 005 B4 relates to a lighting device for vehicles, having a housing and a translucent cover pane that covers a light exit opening of the housing and that can be fastened on the housing by means of a plurality of latching connections distributed over the circumference of the latter, and a plurality of centering devices that are distributed over the circumference of the cover pane that are provided for aligning the cover pane with reference to the housing in a fashion transverse to the mounting direction. It is provided in this case that the centering devices and the latching connections are arranged offset from one another on the circumference of the cover pane, and that after a relatively short mounting path the centering devices are effective as the mounting path to latch the latching connections, the mounting path for the cover pane and the mounting path of the latching connections being the same. This design is intended to have the advantage that the functions of the alignment of the cover pane, which is effected by the centering devices, and of the fastening of the cover pane, which is effected by the latching connections, are separate. Moreover the cover pane should be aligned by the centering devices before it is fastened so that it can be fastened reliably in an exactly aligned position.
In a preferred refinement, there is arranged on the housing in addition to the latching connections at least one resilient latching arm that can be latched on the cover plate transverse to the mounting direction thereof, the latching of at least one latching arm being performed after a shorter mounting path than the mounting path that is required to latch the latching connections. The aim of this design is to enable preliminary fastening of the cover pane on the housing so that when being assembled the lighting device can, after preliminary mounting of the cover pane, be moved on further to a subsequent mounting station without there being the risk of the cover pane being removed from the housing again.
DE 197 19 832 A1 describes a vehicle luminaire in the case of which a front lens is fastened mechanically on a lamp body by means of a fastening device that is formed beyond the boundary between a wall, forming a sealing depression, and the front lens while a sealing lip region of the front lens is being inserted into the sealing depression provided with a sealing means. The fastening device comprises stopper protuberances that are formed on the wall of the lamp body that form the sealing depression, and tongue-shaped elastic parts that are formed on the sealing lip region and have openings. When the sealing lip region is inserted into the sealing depression to mount the front lens in the lamp body, the tongue-shaped, elastic parts are pressed against the stopper protuberances and thereby deformed elastically outwards. The stopper protuberances would then engage smoothly with the openings such that the sealing lip region would not fall out of the sealing depression without the need for a leaf spring.
The two documents DE 197 22 005 B4 and DE 197 19 832 A1 are in essence arrangements in which diffusing screens are fastened mechanically but do not permit mounting with a simple possibility of adjustment.